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The role of forest pests and diseases

– expected future changes

Webinar: Cross-border monitoring and forecasting of forest fires and biodiversity losses 26.5.2021

Tiina YliojaLuke, Forest Health and Biodiversity Group, Helsinki

27.5.2021

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Expected future changes

• Increase in temperature

• Longer growing seasons

• Soil doesn’t freeze as deeply

or long period as earlier

• Increased precipitation

• Soil dryness increases due

to increased evaporation

(especially spring and early

summer)

27.5.2021

Climate change

CO2

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Insects and diseases

Rule of thumb

• insects (poikilotherms) benefit from warming

• diseases benefit from moisture (sporulation)

However, it is never “black and white”

Environmental change affects also performance of

insects and diseases via host plants and natural enemies

Forest structure plays

a role as well

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44 27.5.2021

Spruce bark beetle, Ips typographus

Why the species benefits:

Directly warmer summers increase the development rate from

egg to adult (~700 dd temperature sum), it can attack more trees

per season as the second generation also develops as the growing

season gets longer (~1500 dd)

Indirectly via host trees

Host tree condition, bark beetle attack success depends on the

defense level of the tree: damaged or drought stressed trees

provide lower resin defenses against the beetles. This results higher

population size that can also overcome with the resin defenses of

the healthy trees. Beetles vector the blue stain fungi that aid them

in tree colonization. © Ylioja / Luke

© Luke / Oksanen

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Root rot Heterobasidion annosum ja H. parviporum

Wood decay causing Heterobasidion species are

not sensitive to dry conditions as they habit the

soil.

Heterobasidion parviporum

root and butt rot in spruce

increasing temperatures will increase spore

dispersal

Growth rate of mycelia will increase, faster spread

within infested site

Lack of soil frost will increase root damages and

thus, pathways for infection.

Becomes more abundant in the north that earlier

Yleistyy aiempaa pohjoisempana.

Heterobasidion annosum

root and butt rot in pine (also in spruce)

especially south-eastern part of Finland

pines dry and die

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Heterobasidion

parviporum

Heterobasidion

annosum

© Luke

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Spruce bark beetle (SBB), Ips typographus

Shallow rooted spruce

Lack of soil frost

Increase in root rot occurrence

Risk for wind damage increases

In the eastern and northern

Finland winter precipitation

causes snow damage

Stem breakage

Bending

Up-rooting (no soil frost)

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Host material for the

bark beetle reproduction

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Spruce bark beetle

Transition from endemic state to

epidemic state in current climate

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Endemic Epidemic

Attacks

on

nearby

healthy

trees

Photos: Tiina Ylioja / Luke

Time

# b

eetles

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Pheromone trap monitoring of spruce bark beetle

2012 ->

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Thunderstorms in 2010

Source: doi:10.1111/gcb.15679

Senf and Seidl (2021). Storm and fire

disturbances in Europe: distribution

and trends. Global Change Biology

Photo: Markku Rantala / Luke

Luke / Melin

2020

2021 planned

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To be prepared in current and near future climate

Forest Damages Prevention Act 1087/2013 (currently

being renewed): precautionary measures against spruce

bark beetle (and root rot).

Remove host material before emergence (700 dd) to

prevent the beetles from spreading to surrounding forest

- timber with bark

- damaged trees including

- freshly attacked trees by SBB

27.5.2021Photo: Tiina Ylioja / Luke

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At endemic state

Effort to remove infested trees to

prevent further spread, small resolution

Sanitation felling:

effort to remove freshly attacked trees to prevent

the beetles further spreading 27.5.2021

Photo: Evgeny Lopatin / Luke

Photo: Tiina Ylioja / Luke

1111 27.5.2021

Small scale remote sensing

In 2020 we tested UAV

mounted multispectral

camera to detect bark

beetle infested trees.

Satellite images have not

turned useful for finding

bark beetle infestations in

Finland, yet. Infestations,

groups of dead trees, are

small.

27.5.2021

Slide presented by E. Lopatin 2020/12/01

Hanna Huitu

Evgeny Lopatin

Tiina Ylioja

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At epidemic state

• In the future, warm summer

temperatures not only allow a 2nd SBB

generation to emerge before winter

but also periods of drought will play

larger role in building up spruce bark

beetle epidemics

• Similar conditions are also perquisite

for forest fires

• The need for remote monitoring and

inventory of forest damages will

increase

• From a biodiversity point of view SBB

killed trees that no longer host SBB

could be left to the forest without any

further risk of SBB spreading from them.

• Large scale SBB calamities, such as seen

in Central Europe, can also provide fuel

for forest fires if not salvage logged.

• Salvage logging: effort to remove trees

for timber, to salvage the wood.

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Cross-border collaboration and remote sensing of

forest damages

• Warming climate increases both abiotic

and biotic damage risks (not all of them,

though)

• Pine defoliators such as pine beauty moth

(Panolis flammea), pine looper moth

(Bupalus piniarius) and pine sawflies

(Neodiprion sertifer, Diprion pini) are likely

to increase their abundance as well as

defoliators of birch. The nun moth

(Lymantria monacha) is extending its

range and abundance

• New invasive alien species are a common

concern, e.g. such as emerald ash borer,

Agrilus planipennis

Insects and diseases do not respect

borders

Large windthrow areas, snow damaged

areas in the vicinity of the border, on either

site, are likely to induce secondary insect

damages to both countries.

27.5.2021

Kiitos!

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